Apparatus and method for plating solution analysis

ABSTRACT

A method and apparatus for analyzing plating solutions. The apparatus generally includes a plating cell, a reference electrolyte input, one or more external additive pumps, and a process controller. In one embodiment, the plating cell includes a cavity therein having a larger volumetric portion adjacent a smaller volumetric portion adapted to hold one or more solutions therein. The plating cell also includes a base disposed adjacent the bottom of the plating cell and adapted to receive and mix one or more test solutions as part of the plating solution analysis. In one configuration, the base includes electrical ports adapted to connect stimulation signals to a working electrode, counter electrode, and reference electrode disposed within the cell. The base also includes a thermal sensor in thermal contact with test solutions contained within the vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 10/287,901, filed Nov. 4, 2002 (APPM/006884). Theaforementioned related patent application is herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to an apparatus and methodfor conducting chemical analysis of substrate plating solutions.

2. Description of the Related Art

Metallization of sub-quarter micron sized features is a foundationaltechnology for present and future generations of integrated circuitmanufacturing processes. More particularly, in devices such as ultralarge scale integration-type of devices, i.e., devices having integratedcircuits with more than a million logic gates, the multilevelinterconnects that lie at the heart of these devices are generallyformed by filling high aspect ratio interconnect features with aconductive material, such as copper or aluminum, for example.Conventionally, deposition techniques such as chemical vapor deposition(CVD) and physical vapor deposition (PVD) have been used to fillinterconnect features. However, as interconnect sizes decrease andaspect ratios increase, efficient void-free interconnect feature fill byconventional deposition techniques becomes increasingly difficult. As aresult thereof, plating techniques, such as electrochemical plating(ECP) and electroless plating, for example, have emerged as viableprocesses for filling sub-quarter micron sized high aspect ratiointerconnect features in integrated circuit manufacturing processes.

In an ECP process, for example, sub-quarter micron sized high aspectratio features formed into the surface of a substrate may be efficientlyfilled with a conductive material, such as copper. ECP plating processesare generally two stage processes, wherein a seed layer is first formedover the surface and features of the substrate, and then the surface andfeatures of the substrate are exposed to a plating solution, while anelectrical bias is simultaneously applied between the substrate and ananode positioned within the plating solution. The plating solution isgenerally rich in ions to be plated onto the surface of the substrate,and therefore, the application of the electrical bias causes these ionsto be reduced and thereby plated onto the seed layer. Furthermore, theplating solution generally contains organic additives, such as, forexample, levelers, suppressors, and accelerators configured to controlthe plating distribution throughout the plating process. These additivesare generally maintained within narrow tolerances, so that therepeatability of the plating operation may be maintained.

Conventional ECP systems generally utilize a cyclic voltammetricstripping (CVS) process to determine the organic additive concentrationsin the plating solution. More particularly, three electrodes, a workingelectrode, a counter electrode, and a reference electrode, are immersedin a cell having a plating solution to be measured therein. Thereference electrode and the working electrode are typically connected toa device for measuring the electrical potential difference between therespective electrodes. The reference electrode generally consists ofthree components, a half-cell electrode, a half-cell electrolyte, and areference junction. As used herein, the term “half-cell electrode”generally refers to a solid phase, electron-conducting contact withinthe half-cell electrolyte, at which contact a half-celloxidation-reduction reaction occurs that establishes a stable potentialbetween the half-cell electrolyte and the working electrode. Directphysical, and therefore electrical contact between the half-cellelectrolyte and the sample plating solution is established through thereference junction, which usually consists of a porous ceramic, glass,or plastic plug (e.g. frit), or other device capable of achieving afluid mechanical leak having pores large enough to allow equal transportof anions and cations. The reference junction is necessary to establishelectrical contact with the plating solution, and therefore, the workingelectrode. Conventionally, the potential of the working electrode isswept through a voltammetric cycle that includes both a metal platingrange and a metal stripping range. The potential of the workingelectrode is swept through at least two reference baths of non-platingquality, and an additional bath where the quality or concentration oforganic additives therein is unknown. In this process, an integrated orpeak current used during the metal stripping range may be correlatedwith the quality of the non-plating bath. As such, the integrated orpeak current may be compared to the correlation of the non-plating bath,and the quality of the unknown plating bath determined therefrom. Theamount of metal deposited during the metal plating cycle and thenre-dissolved into the plating bath during the metal stripping cyclegenerally correlates to the concentration of particular organics in theplating solution. CVS methods generally observe the total copper ionsreduced on an electrode over a predetermined potential range. Inasmuchas accelerators or brighteners counteract the suppressors to increasethe plating rate, their quantities may be determined from observationusing standard addition or dilution titration techniques.

Generally, measured quantities of additives are injected from the top ofthe cell into the plating solution using syringes or tubes for testingthe plating solution. Unfortunately, as test volumes may vary from a fewmilliliters to several hundred milliliters, the cell size must bechanged accordingly to accommodate the differing test volumes. Further,as tubes or syringes are used to inject the additives into the platingsolutions, it is difficult to accurately inject a microliter or less ofthe additives into the plating solutions as the volume of the additivesmust be large enough to be dispensed as a droplet. Micro amounts ofadditives may be injected by immersing the tube tips into the platingsolution. However, residual additives contained within the tubes maydiffuse out into the reference bath during the test and contaminate themeasurement. Accordingly, due to the potential variation of additivesdue to the imprecise injections, a plating solution under test may beincorrectly analyzed and therefore cause a plating problem that mayaffect several batches of substrates affecting the plating throughput,and may ultimately increase the cost of production.

As such, there is a need for an efficient and cost effective apparatusand method for plating solution analysis.

SUMMARY OF THE INVENTION

Embodiments of the invention generally provide an apparatus foranalyzing one or more solutions used in a plating process. In oneembodiment, the invention provides an apparatus for analyzing platingsolutions, wherein the apparatus includes a vessel defining a cavityhaving a larger volumetric portion adjacent a smaller volumetricportion. Generally, the larger and smaller volumetric portions areadapted to hold solutions. The apparatus further includes a rotatingelectrode disposed within the cavity, and a fluid injection apparatuscoupled to a bottom portion of the vessel adjacent the smallervolumetric region, wherein the fluid injection apparatus is adapted toinject one or more fluids into at least some of the one or moresolutions.

In another embodiment, the invention provides an apparatus for analyzingplating solutions used in a substrate plating process. The apparatusincludes a vessel defining a cavity adapted to hold the platingsolutions, a rotatable working electrode extending at least partiallywithin the cavity, and a motor disposed on top of the vessel and adaptedto rotate the working electrode. The apparatus further includes a basecoupled to a lower portion of the cavity adjacent a bottom portion ofthe vessel, wherein the base includes a plurality of fluid ports forcoupling fluids from external fluid sources to the cavity. The basefurther includes a connection member having an upper surface incommunication with at least a portion of the cavity, and a fluidjunction disposed within the upper surface of the connection member andadapted to combine fluids from the plurality of fluid ports with one ormore test solutions. The apparatus further includes a counter electrodedisposed parallel to and higher than the working electrode. Theapparatus also includes a reference electrode disposed within the baseand adapted to couple reference electrolyte fluid to one or moresolutions, and a process controller in communication with the system tocontrol the analysis process thereof.

In another embodiment, the invention provides a system for analyzing oneor more plating solutions used in a substrate plating process. Thesystem-includes a plating cell disposed on a frame having a basethereon. The plating cell includes a conical cavity portion adjacent thebase. The base is adapted to couple a plurality of solutions to theplating cell. The system further includes a motor coupled to the platingcell and adapted to rotate a working electrode therein, and a pluralityof pumps disposed on the frame and in fluidic communication with thebase. The system further includes a heat exchanger disposed on theplating cell and adapted to control temperatures of the one or moreplating solutions, and a process controller coupled to at least one ofthe plating cell, heat exchanger, and pumps, wherein the controller isadapted to control the plating cell, the heat exchanger, and the pumps.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the inventionare attained can be understood in detail, a more particular descriptionof the invention, briefly summarized above, may be had by reference tothe embodiments thereof, which are illustrated in the appended drawings.It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention, and are therefore, not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates a perspective view of one embodiment of a platingsolution analysis apparatus for use with aspects of the invention.

FIG. 2A illustrates a perspective view of one embodiment of a platingcell for use with aspects of the invention.

FIG. 2B illustrates a partial side view of a heat exchanger of FIG. 2A.

FIG. 3 illustrates a perspective view of one embodiment of a platingcell base.

FIG. 4 illustrates a diagrammatic view of one embodiment of a referenceelectrode configuration for use with aspects of the invention.

FIGS. 5A and 5B illustrate a simplified view of one embodiment of a heatexchanger used with aspects of the invention.

FIG. 6 illustrates one type of stimulation waveform for use with aspectsof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a perspective view of a plating solution analysisdevice 105 useful in practicing the invention. In one embodiment, theplating solution analysis device 105 includes a frame 101 that may bedivided into functional sections to allow for ease of service and toseparate electronic devices from fluids used during testing. The basicsections include a test section 103, a rear electronics section 106, anda grab sample compartment 107. In one aspect, the plating solutionanalysis device 105 includes a plating cell 108 disposed on the frame101 within the test section 103. The plating cell 108 is described belowwith respect to FIG. 2A. In one configuration, the plating solutionanalysis device 105 may include a reference electrolyte container 112used to hold electrolytes, such as potassium chloride or other referenceelectrolytes. A reference electrolyte pump 118 may be adapted to pumpreference electrolytes from the reference electrolyte container 112 tothe plating cell 108 at the start of the analysis process. The platingsolution analysis device 105 may also include a cell water valve 110adapted to control the flow of water, such as de-ionized water, fromexternal sources (not shown) through a water regulator 116 into theplating cell 108. One or more additive pumps 128 may be disposed on theframe 101 and are adapted to pump solutions, additives, and othertesting fluids from external solution containers, such as syringes,through a sample selector valve 120. Plating cell 108 may be fluidlycoupled to waste pump/valves 122 disposed on the frame 101 to pump wastefluids therefrom. As illustrated, a potentiostat 126 may be disposed ona wall 102 of the frame 101 to shield the potentiostat from any solutionsplashing. The potentiostat 126 may be adapted to control the energyinput of the plating cell 108.

In one configuration, the plating solution analysis device 105 may becoupled to a data processing system 109. The data processing system 109may include a computer or other controller adapted to analyze anddisplay input/output signals of the plating solution analysis device105, and may display the data on an output device such as a computermonitor screen. In general, the data processing system 109 may include acontroller, such as programmable logic controller (PLC), computer, orother microprocessor-based controller. The data processing system 109may include a central processing unit (CPU) in electrical communicationwith a memory, wherein the memory may contain a plating solution testingprogram that, when executed by the CPU, provide instructions forcontrolling the plating solution analysis device 105. The platingsolution testing program may use any one of a number of differentprogramming languages. For example, the program code can be written inPLC code (e.g., ladder logic), a higher level language such as C, C++,Java, or a number of other languages. As such, the data processingsystem 109 may receive inputs from the various components of the platingsolution analysis device 105 and generate control signals that may betransmitted to the respective components of the plating solutionanalysis device 105 for controlling the operation thereof. For example,the data processing system 109 may be configured to control parameterssuch as the flow rate and the quantity of plating solution dispensedinto the plating cell 108, and the timing and quantity of chemicalsadded to the plating solution by the additive pumps 128.

The plating solution analysis device 105 may utilize a plurality ofsolutions, additives, and other mixtures during testing of a platingsolution. An additive free solution (AFS) may be used as the maincarrier for the additives during testing. For a copper electroplatingsolution, for example, the AFS can include copper sulfate, sulfuricacid, chloride ions, and other known AFS solutions. The additives, whichmay be, for example, levelers, suppressors, accelerators, or otheradditives known in the art, are typically organic materials that adsorbonto the surface of a substrate being plated. Useful suppressorstypically include polyethers, such as polyethylene glycol, or otherpolymers, such as polypropylene oxides, which adsorb on the substratesurface, slowing down copper deposition in the adsorbed sites. Otheruseful suppressors typically include sodium benzoate and sodium sulfite,which inhibit the rate of copper deposition on the substrate. Usefulaccelerators typically include sulfides or disulfides, such asbis(3-sulfopropyl) disulfide, which compete with suppressors foradsorption sites, accelerating copper deposition in adsorbed areas.

FIG. 2A is a perspective view of one embodiment of a plating cell 108.The plating cell 108 includes a vessel 130 supported by a base 160, andcoupled to the wall 102. The vessel 130 is adapted to hold one or moreplating solutions. As such, to minimize absorption and desorbtion of theplating solution and/or additives from/to the vessel walls, the vessel130 may be formed from a low porosity material, such as glass or a lowporosity plastic. The vessel 130 may be configured to allow externalvisibility of the one or more plating solutions. To provide an extendedvolumetric operating range, the shape of the vessel 130 may include alarger top cylindrical section 134 disposed adjacent a smaller conicalbottom section 136 forming a cavity 131. Conical section 136 permits asmall volume of liquid to be used to reach a tip 139 of a workingelectrode 138, while the larger cylindrical top section 134 allowslarger volumes to be accommodated, such as required for dilutions. Forexample, the vessel 130 may be configured to analyze test solutionvolumes from about 20 ml to about 100 ml.

The working electrode 138 may be rotatably disposed in the vessel 130and adapted to contact at least some of the test plating solution withinthe cavity 131. The working electrode 138 includes a metal disk 153disposed on the working electrode tip 139. The metal disk 153 mayinclude corrosive resistant metals, such as platinum and gold, forexample, that can be plated and stripped repeatedly without substantialoxidation or dissolution. The metal disk 153 typically has a flat,polished surface between about 2 mm and 7 mm in diameter, and isdisposed about flush on the working electrode tip 139. The metal disk153 is sized at a thickness adapted to sustain one or moreplating/stripping processes. The working electrode 138 further includesa rotating electrical contact end 148 distal a solution contact end 150disposed within the cavity 131. The rotating electrical contact 148 maybe configured to allow the working electrode 138 to rotate about itslongitudinal axis, while providing a continuous electrical contact withthe potentiostat 126 (See FIG. 1). The working electrode 138 isgenerally mounted in an axial position using a lower and upper bearing140, 141 axially aligned with the longitudinal axis of the workingelectrode 138 and disposed within a plating cell cap 142. In oneconfiguration, the plating cell cap 142 is disposed above the largersection 134 of the vessel 130 to allow the working electrode 138 toextend from the plating cell cap 142 though a lid 144. The lid 144 mayinclude a spray nozzle 146 thereon to dispense water within the cavity131 from a fluid coupling 151.

The plating cell cap 142 includes a motor unit 132. In one aspect, toestablish relative motion between the working electrode 138 and the testplating solution, the motor unit 132 includes a motor 152 typically usedto rotate the working electrode 138. The rotating working electrode 138may in effect “stir” the test plating solution to allow a fresh supplyof test plating solution to encounter the surface of the workingelectrode 138. Without such relative motion between the test platingsolution and the working electrode 138, the test plating solutionbecomes depleted at the surface of the working electrode 138 and thedeposition rate obtained will not reflect the correct plating rate forthe test plating solution. The motor 152 may be positioned within theelectronics section 106 (See FIG. 1) to minimize mechanical interferencewith the plating cell 108 and avoid contact with fluids. To rotate theworking electrode 138, a shaft 155 of the motor 152 may be coupled tothe working electrode 138 via a drive belt system 154. The drive beltsystem 154 may include a motor pulley 156 attached to the shaft 155 andan electrode pulley 157 mounted between the lower and upper bearings140, 141 to the working electrode 138. In one aspect, one or more drivebelts 158 couple the motor pulley 156 to the electrode pulley 157 tocouple the motor rotation to the working electrode 138. In anotheraspect of the invention, the motor 152 is adapted to provide arotational rpm range between about 100 rpm to about 4000-rpm and may beadjusted in incremental rpm steps of about less than about 10 rpm perstep. While the motor 152 may be a DC motor, other motor types arecontemplated.

FIG. 3 is a perspective view of one embodiment of a base 160 used tocouple fluids to the vessel 130. FIGS. 1 and 2 are referenced as neededin the discussion of FIG. 3. The base 160 is coupled to the vessel 130via a connection member 162 adapted to allow the base 160 to beseparated from the vessel 130 when needed, such as for example, whenbeing cleaned. While the base. connection 162 may be configured as aninterference fit, using the friction between a mating connection 129(See FIG. 2A) in the vessel 130 and the connection member 162 to form aseal therebetween, other types of connections are contemplated such as athreaded connection. In one configuration, the base 160 is formed of arelatively non-porous material such as ceramics, polymers, e.g., Teflon,and other materials employed to minimize absorption and desorbtion ofthe test plating solution and/or additives from/to surfaces of the base160 and the connection member 162 in contact therewith.

In one aspect, the base 160 includes a counter electrode receptacle 164adapted to receive a counter electrode 166. The counter electrode 166may be slidably disposed within the counter electrode receptacle 164 toallow removal of the counter electrode 166 for cleaning or replacement,for example. The counter electrode 166 further includes a head member167 distal the counter electrode receptacle 164, and in about axialalignment with the working electrode 138 (see FIG. 2A). In oneconfiguration, the head member 167 may be aligned with the workingelectrode tip 139 for a more uniform charge distribution, and may besized somewhat larger than the working electrode area to minimize thecurrent density on the surface of the head member 167. The counterelectrode 166 may be formed or plated with materials resistant tocorrosion in oxidizing and/or reducing conditions such stainless steel,for example. As the connection member 162 is made of generally pliablematerial allowing the receptacle diameter to vary under externalpressure, the diameter of the counter electrode receptacle 164 may besized to seal against the edge of the head member 167 when theconnection member 162 is compressed when inserted into the matingopening 129. The counter electrode receptacle 164 may include a bore 181at a distal end. The bore 181 includes an insertion opening 186 to allowthe use of a tool, such as a pin, to push on the counter electrode 166on an end distal head member 167, to easily remove the counter electrodefrom the counter electrode receptacle 164.

In one configuration, the base 160 includes one or more fluid ports 127(only four are shown) adapted to couple fluids between the base 160 andexternal fluid sources and/or storage facilities, such as syringes, andfluid removal systems for waste fluid removal. In one configuration, thefluid ports 127 are adapted to receive external tubing interconnects(not shown) configured to provide a seal between the ports 127 and theexternal tubing. As shown, two of the fluid ports 127 converge into afluid hub 170 to combine at least one additive with the AFS to form atest plating solution (e.g., a test solution). Although for clarity onlytwo fluid ports 127 are shown connected to the fluid hub 170, one ormore fluid ports 127 may be coupled to the fluid hub 170. The fluid hub170 is coupled to the vessel 130 through a chamber 171 described below.In one operational aspect, when combining precise small volumes ofadditives with the AFS, it is important to keep the additives fromdiffusing or flowing into the AFS or into the test solution until theadditives are needed. For this purpose, the fluid ports 127 may bepositioned so that the AFS fluid from one fluid port 127 does not flowby density-driven convection into another fluid port 127. In one aspect,this is done by keeping the fluid port 127 coupled to the higherspecific gravity fluid lower than the other fluid ports 127. Forexample, if the AFS has a higher specific gravity relative other fluids,the fluid port 127 supplying the AFS to the fluid hub 170 may be placedlower relative other fluid ports 127 coupled to the other fluids. Inanother aspect, the fluid paths between fluid ports 127 and hub 170 areangled (i.e., sloped) downward into the more dense solution so that thelighter fluid within it is not exchanged by convention with the solutionin the hub 170. In another aspect, the fluid ports 127 may be adaptedsuch that the fluid in the fluid ports 127 may be drawn back into arespective fluid port 127 to form an “air plug” when the one or morefluids are slightly retracted from the fluid hub 170 while it is empty.The air plugs keep the fluids isolated from the transport solution influid hub 170 and in turn from the test solution. The chamber 171 mayalso be sized a sufficient length to prevent diffusion from an additivein the chamber 171 from reaching the test solution contained in thevessel 130 within the time duration of a test. For example, if a testduration where one hour long, the chamber 171 may be sized so that ittakes more than one hour for diffusion from an additive to reach thevessel 130. Thus, the fluid ports 127 may be used to control theintroduction of fluids into the fluid hub 170, isolate fluids from thetest solution, fluidically impede diffusion between the fluids and theAFS, and fluidically impede diffusion of the fluids into the testsolution.

In one configuration, the fluid hub 170 may be used to combine fluids toproduce mixtures with high dilution ratios. Higher dilution ratios mayenable increased measurement precision where small doses of additives orsolutions are used. The fluid ports 127 and fluid hub 170 may be used tocombine a sample or additive and simultaneously draw the combinedmixture from the vessel 130 into a mixing coil (not shown). The mixingcoil may be coupled to a fluid port 127, and used to supply the mixtureto the vessel 130 during analysis. The mixing coil typically consists ofa length of tubing, tightly wound into a coil that may be about five toten turns long. Drawing solution into and through the mixing coil mixesa combination of fluids, such as is needed for serial dilution. Serialdilution may be done by simultaneously injecting fluids into fluid hub170 while at about the same time, drawing them out the opposite end ofthe coil into a reservoir, such as a syringe pump, which is then used todeliver the mixture. Alternatively, the additives and solutions may alsobe combined by the fluid hub 170, dispensed into the vessel 130, mixedby the rotating action of the working electrode 138, and then drawn backthrough the fluid hub 170 into a container (not shown) such as a syringepump to premix a test solution.

To help dislodge air bubbles that may be trapped at the surface of theworking electrode tip 139, the chamber 171 couples the fluid hub 170 toa liquid port 172 angled upward and about toward the center of theworking electrode tip 139. A test plating solution from the liquid port172 provides a fluid stream to “sweep” the air bubbles from theelectrode tip 139 during the filling of vessel 130. This allows airbubbles to be swept from the downward facing working electrode tip 139.This is in contrast to the conventional top fill approach where airbubbles may be trapped as the solution level rises past the workingelectrode.

To allow efficient fluid removal after a test, the connection member 162may be coupled to a fluid waste port 173 using a fluid exit port 175disposed on surface 169 of connection member 162. The fluid exit port175 may be configured to rapidly flush waste solutions when required.The fluid exit port 175 may have an oblong cross section adapted toallow sufficient liquid surface tension to keep the test platingsolutions from escaping during a testing process, while having across-sectional area sized to allow rapid removal of the testingsolutions when desired though the fluid waste port 173.

The base 160 may include a plurality of electrical connections toprovide stimulation signals to and from the base 160 and controller 109.An electrical connection port 165 is adapted to receive electricsignals, such as current from a potentiostat 126 (See FIG. 1), to powerthe counter electrode 166. A replaceable contact pin 168 (See FIG. 2A),illustrated in a disconnected position, when in contact with the counterelectrode 166, conducts an electric bias to the counter electrode 166from an external source (not shown). It is contemplated that the contactpin 168 may be spring-loaded to urge the contact pin 168 against thecounter electrode 166 to provide lower electrical contact resistance.The base 160 may also include a reference electrode port 176 adapted toconduct reference current to a connecting wire described below withreference to FIG. 4 described below.

A thermal sensor 174, such as a thermistor or other thermal detectiondevice, may be disposed in thermal contact with the counter electrode166 to provide a temperature measure of the plating solution beingtested. The thermal sensor 174 may be positioned proximate the undersideof the head member 167 to provide improved thermal conduction with thetest plating solution. The thermal sensor 174 may be coupled to anexternal temperature sensor circuit (not shown) using the temperaturesensor port 177.

With reference to FIGS. 3 and 4, the base 160 may also include areference electrode port 176 to receive a reference electrode 178. Thereference electrode 178 may be a saturated Calomel reference wireelectrode (SCE) or silver lined with silver chloride, for example. Inone configuration, the reference electrode 178 may be formed from aconnecting wire 184, such as a silver/silver chloride wire having asilver chloride layer 187 thereon. The connecting wire 184 is connectedto a potentiostat 126 (See FIG. 1), through the reference electrode port176. The potentiostat 126 keeps the voltage between the workingelectrode tip 139 and the reference electrode 178 constantlyproportional to a signal from controller 109. The potentiostat 126accomplishes this by varying current between the counter electrode 166and working electrode tip 139. In another mode, the potentiostat 126 isswitched to work as a galvonostat where the current between the counterelectrode 166 and the working electrode tip 139, is kept proportional toa signal from the controller 109. In this mode, the voltage potentialbetween the working electrode tip 139 and reference electrode 178 isrecorded by the controller 109.

As illustrated in FIG. 4, the reference electrode 178 may be disposed ina reference electrode chamber 180. The reference electrode chamber 180is coupled on one end to a reference solution port 182, and on anopposing end 183 to a z-shaped chamber 185. The z-shaped chamber 185couples reference solutions (i.e., conductive salt solutions) from thereference electrode chamber 180 to the chamber 171 through a referencefluid junction 188. Sections of the z-shaped chamber 185 may be inclinedto prevent density-driven fluid exchange between the reference solutionand the test plating solution within the chamber 171 to minimizecross-contamination. The chamber 171 may be sized to increase thediffusion time of the electrolyte salts to minimize the effects ofdiffusion. The z-shaped chamber 185 may also include a constrictedsection 189 sized to impede the reference solution and test platingsolution exchange. The reference fluid junction 188 is sized to allowcommunication between the reference solution and the testing solutionand to prevent changing junction potential due to clogging. Duringtesting, to minimize the reference solution contamination with the testplating solution, while allowing the reference solution and test platingsolution to make electrical contact, the reference solution flow isstopped within the reference electrode chamber 180 and the z-shapedchamber 185 to form a conductive slug between the electrode chamber 180and testing solution. In another configuration, the reference solutionis delivered at a lower end of the reference electrode 178 from thereference solution port 182 and is pumped vertically about the referenceelectrode 178 to assist in the entrainment and removal of air bubbles.In an alternative configuration, the chamber 189 may be coupled to thefluid exit port 175 to combine the reference solution with a testplating solution therein. This isolates the reference solution from thetest plating solution in the vessel 130, particularly to stirredsolutions within the vessel 130, while preventing diffused electrolytesalts from being carried into the test plating solution during theaddition of additive doses.

In order to maintain a desired temperature of a test plating solution, aheat exchanger 190 and thermo-electric module 192 may be disposed inthermal contact with the vessel 130 as illustrated in FIG. 2A and 2B.For improved thermal contact, the thermoelectric module 192 may bedisposed in contact with a flat area of the vessel 130. The heatexchanger 190 may generally include a coolant input 191 to acceptcoolant from a coolant valve 114 (see FIG. 1). In one aspect, asillustrated in FIG. 2B, the heat exchanger 190 includes one or more ofthe thermo-electric modules 192 sandwiched between the heat exchanger190 and the vessel 130 to allow the test plating solution to be broughtabove, and below, ambient temperature. FIGS. 5A and 5B illustrate twoembodiments 190A and 190B of heat exchanger 190. Heat exchangers 190Aand 190B reflect trade offs between lower cost and a more compactdesign, respectively. In one configuration, the process controller 109controls the thermo-electric module 192 in a loop process using thethermal data derived from the thermal sensor 174 to maintain a desiredtest plating solution temperature.

Embodiments of the invention further provide cyclic or plusevoltammetric methods for measuring the concentration of additives in aplating solution. The methods generally include pumping electrolytesolution from the reference electrolyte pump 118 into the referenceelectrode chamber 180 and z-shaped chamber 185. The vessel 130 iscleaned and a carrier solution (e.g., AFS) along with the sample of theplating solution, and one or more additives, is pumped from the fluidports 127 through the fluid hub 170 and through the liquid port 172 toform a test solution in the vessel 130. A small volume of additives maybe added (e.g., 5 micoliters) before the addition of a carrier solution,which is subsequently added to flush the additive into the vessel 130 tocreate a liquid plug, or gap within the chamber 171. The liquid plugisolates the additive supply from the test plating solution, thuspreventing diffusion of the additive from altering test results duringtesting. The methods further include cycling the potential of theworking electrode 138 through a series of steps while measuring currentto determine the amount of additives present. The methods also includessteps such as a stripping, cleaning, pre-plating, equilibration, andmetal deposition step. For example, the metal stripping step includespulsing a potential between the working electrode 138 and the referenceelectrode 178 between an initial voltage and a metal strippingpotential, until the corresponding stripping current is approximately 0mA/cm. As used herein, the term “pulse” refers to immediately applying adesired potential from a prior potential. Next, the potential is pulsedbetween an initial potential and a cleaning potential to clean theworking electrode 138 in the cleaning step. A thin layer of metal isthen plated onto the surface of the working electrode 138 in apre-plating step by pulsing to a pre-plating potential. The potential isthen pulsed back to the initial potential in an equilibration stage. Thefinal step is a metal deposition step. The deposition step includesscanning to an additive sensitive potential, i.e., a potential where theadditive desorbs from the working electrode, holding the additivesensitive potential, and reversing the potential and scanning back tothe open circuit potential. As used herein, the term “scanning” refersto either linear or pulsed ramping to a desired potential from a priorpotential. The additive sensitive potential may vary and is dependent onthe additive to be measured. FIG. 6 illustrates one example of a pulsedramp waveform 600 used to perform voltammetric organic analysis of atest plating solution with the plating solution analysis device 105. Thewaveform 600 includes a plurality of anodic and cathodic pulses adaptedto provide either a controlled current or potential to the workingelectrode 138. In one aspect, the waveform 600 is formed from aplurality of varying pulses 604 that correspond to a range of workingelectrode current or potential.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A system for analyzing one or more plating solutions used in a substrate plating process, comprising; a plating cell disposed on a frame having a base thereon, wherein the base is disposed adjacent a conical bottom cavity portion of the plating cell and adapted to couple a plurality of solutions to the plating cell; a motor coupled to the plating cell and adapted to rotate a working electrode therein; and a plurality of pumps disposed on the frame and in fluidic communication with the base, the pumps are adapted to pump the one or more solutions to the base, wherein the one or more solutions are combined within the base and plating cell to define a test plating solution to be analyzed.
 2. The system of claim 1, wherein the plating cell comprises an upper cavity portion having a larger volume than the conical cavity portion.
 3. The system of claim 1, wherein the base comprises a plurality of fluid ports thereon adapted to couple one or more fluids from the fluid pumps to the plating cell.
 4. The system of claim 3, wherein the fluid ports are coupled to a fluid junction adapted to combine one or more fluids pumped into the fluid ports into the test plating solution.
 5. The system of claim 3, wherein the fluid ports are coupled to a fluid junction adapted to direct a stream of the one or more solutions toward the working electrode to dislodge air bubbles therefrom during a fill process.
 6. The system of claim 5, further comprising a heat exchanger disposed on the plating cell and adapted to control a temperature of the one or more plating solutions.
 7. The system of claim 6, wherein the heat exchanger comprises a thermoelectric heat module in thermal contact with the plating cell and adapted to control a temperature of the one or more solutions.
 8. The system of claim 6, further comprising a process controller coupled to at least one of the plating cell, the heat exchanger, and the pumps.
 9. The system of claim 8, wherein the process controller is adapted to control a potentiostat to drive one or more stimulus signals between the working electrode and a counter electrode disposed in the base.
 10. The system of claim 8, wherein the process controller is adapted to receive a reference signal from a reference electrode disposed in the base.
 11. The system of claim 8, wherein the process controller is adapted to control at least one operation of the plating cell, the heat exchanger, thermoelectric modules, and the pumps.
 12. The system of claim 1, wherein the base comprises a fluid exit port having an oblong cross-section adapted to provide a desired surface tension to prevent leakage of the one or more plating solutions from the plating cell prior to discharge, and provide a rapid discharge when the one or more plating solutions are discharged from the plating cell.
 13. A method of analyzing solutions used in a plating process, comprising: receiving at least one fluid and at least one solution into a fluid hub; mixing the at least one fluid and at least one solution in the fluid hub to form a test solution; delivering the test solution to a vessel; isolating the at least one fluid and at least one solution from each other; providing a liquid plug of the at least one solution between the fluid hub and the test solution contained in the vessel; providing an electrolyte slug in contact with a reference electrode; wherein the electrolyte slug is in contact with the test solution; and testing the test solution.
 14. The method of claim 13, wherein receiving comprises providing a plurality of fluid delivery paths to couple external fluids to the fluid hub, the fluid delivery paths are configured to fluidically inhibit the intrusion of the at least one solution into the at least one fluid.
 15. The method of claim 13, wherein isolating comprises providing an air plug between the at least one fluid and the test solution.
 16. The method of claim 13, wherein providing the electrolyte slug comprises fluidically inhibiting a flow of the electrolyte between the electrolyte and the test solution.
 17. The method of claim 16, wherein providing an electrolyte slug comprises providing a passage for an electrolyte to contact the test solution, wherein the passage is configured to prevent density driven fluid exchange between the electrolyte and the test solution.
 18. The method of claim 13, further comprising combining a plurality of fluids to form a premixed version of the at least one fluid.
 19. The method of claim 18, wherein combining comprises mixing the plurality of fluids in the fluid hub.
 20. The method of claim 18, wherein combining comprises mixing the plurality of fluids in the vessel. 